The H3-2D manual insists, in bold red font, that I put the camera on the gimbal before putting the gimbal on the Phantom 2. Yet I can find no other reference to that installation order in the instructions, nor does the tutorial video show that.
I set mine up at first without camera and it made no response other than a few odd noises. It says you will strain motors as it attempts to balance. Once the camera was on it auto corrected perfectly.